(a) CO oxidation light-off curves for the transition-metal-substituted
CeO2 samples, measured with 20 mg of the catalysts in 1%
CO balanced with dry air at a flow rate of 12 mL min–1. (b) CO oxidation light-off curves under simulated exhaust conditions
(0.2% CO, 0.01% NO, 0.083% C2H4, 0.033% C3H6, 0.11% C3H8, 6.0% CO2, 12.0% O2, and 6.0% H2O balanced with
Ar) using the CuCoFeNiMn-CeO2 catalyst for three repeated
cycles, measured with 111 mg of the catalyst at a flow rate of 370
mL min–1 (GHSV ≈ 200000 h–1). (c) CO-TPR profiles of the transition-metal-substituted CeO2 catalysts with the CO consumption amount being highlighted.
(d) Evolution of the 18O2 species for CuCoFeNiMn-CeO2 and CuOx-CeO2 during
the TPOIE measurement, where the onset temperature is noted for comparison.